In recent years, the miniaturization of mobile phone terminals has advanced, and to improve the effective use of space and the usability, sliding-type structures in which a housing with a display formed thereon and another housing with a keyboard formed thereon are placed on top of each other have become more common. In such sliding-type mobile phone terminals, for example, a display is provided on the upper housing and a keyboard and the like are provided on the lower housing. In this way, a user can always view the display. Further, by sliding one housing with respect to the other housing in a lengthwise direction or a crosswise direction, the keyboard is exposed, and thereby a user can operate the keyboard.
Meanwhile, in recent years, more and more functions have been incorporated into mobile phone terminals, let alone the telephone call function and the data communication function. For example, terminals equipped with a TV viewing function and a game function have been released, and as a result, the demand for such a feature that a user can view the display from various directions has been growing. That is, in the past when mobile phone terminals have been used only for telephone calls and emails, viewing the display in the portrait position is sufficient for their purposes. However, when they are used for one-seg use, browser use, game use, and the like, a feature that the display can be viewed in a landscape position significantly improves the usability. As a result, nowadays, mobile phones having various structures capable of changing the orientation of the display are being developed.
For example, in mobile phones disclosed in Patent documents 1, 2 and 3, when a first housing on the LCD side is slid, part of the keys arranged on a second housing on the microphone side is exposed. Further, when the first housing is rotated, all the keys arranged on the second housing are exposed. In this way, with the capability of rotating the display, it is possible to dispose some keys, which are used when the first housing is rotated, in the part of the second housing exposed by the rotation. Further, for example, the slid state is used for telephone calls, emails, and the like, whereas the rotated state is used for purposes, for which the lengthwise direction of the LCD is oriented in the horizontal direction, such as one-seg and games.
Further, mobile phones disclosed in Patent documents 4, 5 and 6 are electronic equipment formed by further placing a third housing on the first and second housings. Further, these three housings adopt such a structure that they are connected in a freely movable manner so that they can mutually slide, rotate, and open/close. By adopting the three-tiered structure like this, some keys can be disposed in the middle housing and thereby different keys can be used according to the purpose. For example, keys on the second tier and keys on the third tier can be used according to the orientation of the display.
[Patent Document 1]
    Japanese Unexamined Patent Application Publication No. 2007-116712[Patent Document 2]    Japanese Unexamined Patent Application Publication No. 2005-147401[Patent Document 3]    Japanese Unexamined Patent Application Publication No. 2007-49294[Patent Document 4]    Japanese Unexamined Patent Application Publication No. 2007-179525[Patent Document 5]    Japanese Unexamined Patent Application Publication. No. 2004-40490[Patent Document 6]    Japanese Unexamined Patent Application Publication No. 2007-174617